The present invention relates to an apparatus and a method for forming stabilized atomized microemulsions from different liquids which are normally mutually immiscible, for the most disparate applications in the chemical-pharmaceutical, food, cosmetic sectors et cetera. In particular, the apparatus and the method according to the present invention allow to form microemulsions with untreated and/or basified water of liquid hydrocarbons, with the most disparate densities and viscosities, for use as fuels for civil and industrial heating systems and also for large engines and/or as fuels for Diesel engines.
Apparatuses and methods for forming microemulsions are known in the art.
For example, EP-630,398 discloses the formation of emulsions by mixing components in a static mixer in particular pressure and temperature conditions in the presence of a mixture of surfactants.
EP-124,061 in the name of this same Applicant discloses an apparatus and a method for forming emulsions of fluid fuels with other immiscible fluids, particularly water. The described apparatus is constituted by a turbotransducer which comprises an emulsification chamber in which the fluid fuel and the water are subjected to a combined mechanical and electromagnetic action which generates, inside said chamber, a centered corridor through which the mixed fuel and water flow.
EP-373,353, in the name of this same Applicant, discloses a process for producing stabilized emulsions of a fuel, particularly a fuel for Diesel engines, and water, with the addition of a product which acts as a lubricant and antifreeze, which comprises the premixing of fuel, water and additive and the subsequent passage of the resulting mix through a turbotransducer similar to the one of the above-cited EP-124,061.
The Applicant has found that these methods entail a relatively high energy expenditure with respect to the productivity of the system and have a low need for conversion of the energy associated with the passage through the emulsifying apparatus into surface energy of the particles of the disperse phase.
The aim of the present invention is to provide a system for obtaining stabilized atomized microemulsions which is even more advanced and most of all less expensive, for the purpose of industrialization with a considerable saving in terms of times and costs for production, maintenance, siting and electric power.
Another object of the present invention is to provide an apparatus which can assume any size and therefore can be inserted directly in production line of any required productivity, even if it is a few liters per hour, and for use in the pharmaceutical and/or cosmetic industry.
Another object of the present invention is to provide an apparatus which can work without very expensive and unreliable ultrasound systems or other devices.
This aim, these objects and others which will become better apparent from the following description are achieved by an emulsifying apparatus according to the invention for forming stabilized atomized microemulsions, which comprises a primary chamber and a sequence of at least two cavitation chambers arranged in succession, means for feeding fluids into said primary chamber, and means for the exit toward the outside of said apparatus of the microemulsion from the last cavitation chamber of the sequence of cavitation chambers, said primary chamber and said at least two cavitation chambers being fluid-connected to each other by way of fluid passage means, said passage means being adapted to produce a velocity of the fluids, during passage, which gradually increases from the primary chamber to the last cavitation chamber of the sequence of cavitation chambers.
The apparatus according to the invention includes a reverse-flow diffuser with multiple cavitation chambers, capable of imparting a turbine effect to the fluids. The cavitation chambers can be theoretically unlimited in number and can have the most specific dimensions. In said chambers, the microemulsion takes form from the peripheral region and is perfected in the last cavitation chamber.
The primary chamber can be cylindrical or can also have an oval, square or rectangular cross-section. A polyhedral or triangular cross-section is also possible.
Conveniently, the first cavitation chamber of the sequence of cavitation chambers is at least partially arranged inside the primary chamber and the other cavitation chambers of the sequence of cavitation chambers are is arranged so that each one is at least partially inside the preceding one in the sequence of cavitation chambers.
Advantageously, the cavitation chambers of the sequence of cavitation chambers are each arranged inside the preceding cavitation chambers in the sequence of cavitation chambers, the sequence of cavitation chambers being arranged inside the primary chamber.
In a preferred embodiment, the primary chamber is the container of all the other cavitation chambers installed inside it.
Advantageously, the primary chamber and the cavitation chambers of the sequence of cavitation chambers have substantially parallel axes and are even more advantageously coaxial.
A larger number of cavitation chambers with turbine effect is convenient in the presence of a plurality of secondary fluids with highly contrasting physical and chemical characteristics.
The cavitation chambers of the sequence of cavitation chambers preferably each have a blind wall which is arranged substantially at right angles to the axes of the cavitation chambers and is directed toward the preceding cavitation chamber in the sequence of cavitation chambers.
Preferably, the cavitation chambers of the sequence of cavitation chambers are mutually rigidly coupled and are rigidly coupled to the primary chamber.
The outside of the apparatus, or the surface of the primary chamber, can if necessary be heated for example by means of a self-compensating self-adjusting heating cable and insulated.
The primary cavitation chamber can be made of non-magnetic or scarcely magnetizable steels (AISI 304L, AESI 316L, ASTELLOY C), since if appropriate the system can be activated with magnetic assemblies of lanthanum and/or samarium or cobalt with a high energy yield.
The dimensions of the chamber and the thickness of the walls are chosen according to the productivity required by the user and/or by the process.
Conveniently, the fluid passage means are adapted to impart to the fluids a turbine effect motion.
Preferably, the fluid passage means comprise holes in the walls of the cavitation chambers of the sequence of cavitation chambers.
Advantageously, the holes have longitudinal axes which are inclined with respect to the axis of the corresponding cavitation chamber, the inclination of the axes in the holes of each cavitation chamber of the sequence of cavitation chambers being opposite to the inclination of the axes of the holes of the preceding and subsequent cavitation chambers of the sequence of cavitation chambers.
The number of holes, their cross-section, the inclination of the holes with respect to the horizontal axis, the distance between the surfaces of each chamber, the working volume of each chamber and the total volume of the primary chamber are the basis for the calculations related to the mechanics of obtaining instant stable microemulsions or microcells with assurance of the degree of dispersion of the secondary fluid. In the calculation (volume of chambers, number of holes, cross-section of holes, inclination of holes, distance between the walls of the chambers) it is also necessary to take into high account the chemical-physical parameters of the involved fluids.
For example, the sum of the cross-sections of all the holes of each cavitation chamber should be lower than for the preceding cavitation chamber in the sequence to ensure an increase of the fluid velocity in the holes from the first to the last cavitation chamber in the sequence.
The velocity of the fluids in the holes of the walls of the cavitation chambers gradually increases from the first to the last chamber along the path of the fluid. The velocity in the holes is lower in the holes of the first chamber and can reach even tens or hundreds of meters per second in the holes of the last chamber of the sequence of cavitation chambers.
Preferably, the velocity increase in the holes of the last cavitation chamber with respect to the velocity in the holes of the first cavitation chamber of the sequence of cavitation chambers should not be less than fourfold. Optimally, said increase is greater than eightfold for any characteristic of the fluids.
The means for feeding the fluids into the primary chamber can comprise means for feeding the primary fluid and means for feeding the secondary fluid.
The means for feeding the primary fluid(s) can be preferably constituted, for example, by screw-type electric pumps.
Advantageously, the means for feeding the secondary fluid comprise an injector system equipped with a diffuser shaft provided with holes which are inclined with respect to the longitudinal axis of said stem, the inclination of said holes being such as to allow to propel the secondary fluid into the first cavitation chamber in the opposite direction with respect to the direction in which it enters the shaft.
The holes can have a preferred diameter between 1 and 15 mm, depending on the characteristics of the secondary fluid and on the flow-rate, pressure, viscosity and temperature of the primary fluid.
The outside diameter of the diffuser shaft can vary from 8 to 10 mm up to a reasonable maximum of 150 mm, larger dimensions being possible but seldom feasible or advisable. The total number of holes can vary from a minimum of 24 to a reasonable maximum of 350. The diameter of each hole can vary from a minimum of 1 mm to a technological maximum of 15 mm. The spacing between the axes of each hole can range from a minimum of 5 mm to a maximum of 30 mm.
The holes along the diffuser shaft must be arranged at least on four rows (axially offset by 90xc2x0 with respect to the cross-section of the diffuser shaft) and preferably on six and/or eight rows which are proportionally axially offset.
In order to avoid any reverse flow of primary fluid toward the source of the secondary fluid, it is possible to interpose between the diffuser shaft and the dosage pump fluid outlet a check valve, for example provided with a ball and spring and set from a minimum of 5 kg to a maximum of 25 kg.
In this case, a preliminary operation to be performed is the filling of the body of the check valve with the secondary fluid before starting the pump that conveys the primary fluid.
The secondary fluid is conveyed normally through electric metering pumps of the plunger type with adjustment of the flow-rate by means of a vernier scale which acts on the stroke of the plunger.
The flow-rate of this electric pump or of the electric pumps is calculated in relation to the maximum percentage of secondary fluid to be introduced. When this parameter exceeds 2000-2500 liters per hour, however, it is convenient to split the flow-rate over a plurality of electric pumps, especially in order to handle motors with limited specific power levels and dimensions (no more than 7-8 kilowatts).
Advantageously, the means for feeding the secondary fluid further comprise a metering valve which is arranged between said diffuser shaft and a metering pump for feeding the secondary fluid.
The primary fluid can be fed through an electric pump of the screw and/or gear and/or plunger and/or hollow-disk and/or multiple-disk type. A screw-type electric pump with adjustment of flow-rate and pressure by means of an adjustable bypass is advisable. Centrifugal pumps are not advisable.
The pressure applied to the primary fluid can be, for example, 0.5 to 1 bar and up to 400 bar or more, according to the chemical-physical characteristics of the secondary fluid and according to the characteristics of the electric pumps that convey the secondary fluid, since said pumps must automatically apply a pressure drop delta-p (xcex94p) to the secondary fluid so that it can be introduced in the first primary chamber.
For the sake of convenience, the pressure imparted is the one best allowed by the type of electric pump in relation to its reliability, but also in relation to the physical-chemical characteristics of the working fluids and in relation to the characteristic of the electric pump that conveys the secondary fluid, which has to apply to the secondary fluid a pressure increase of at least 1 and/or 2 bars with respect to the primary pressure in an automatic manner. For this purpose, the secondary pressure feeding assembly that is provided is an electric pump of the pulsating plunger type.
The temperature of the fluids must be the most appropriate in relation to the most appropriate working viscosity of the process fluid and to its chemical-physical content.
As an alternative, the means for feeding the fluids in the first feeding chamber comprise means for feeding the primary fluid and the secondary fluid, possibly pre-mixed but dosed with respect to each other in the most appropriate ratios.
The means for the discharge of the microemulsion from the apparatus conveniently comprise a duct provided with a control valve.
Advantageously, a pressure adjustment device is arranged on the duct in a position which lies upstream of the control valve.
The apparatus according to the invention can be constituted by a particular mechanical assembly with multiple cavitation chambers which are preferably coaxial and are affected by fluids on their outer surface and, through holes formed in the outer surface in appropriate sizes and with angles (with respect to the horizontal axis) evaluated in relation to the characteristics of most of the intended fluids and to the dimensions of the various successive cavitation chambers (optionally arranged one inside the other), propels the fluids that flow through it from the outside inward, diffusing them into all of the occupied volume owing to the very high turbulence.
The process is repeated every time the fluids flow from the primary chamber toward the last cavitation chamber, i.e., in the embodiment with coaxial chambers arranged inside each other, from the outer chamber to the inner chamber. The flow of the mass of fluid, and therefore the process, occur with a path from the outside inward and not vice versa as in the presence of a diffuser which receives the fluid internally and propels it into an external volume, known as direct-flow diffuser. Accordingly, the apparatus according to the invention can be termed reverse-flow diffuser.
The apparatus according to the present invention is adapted for providing a turbine effect in the fluids that flow through it; this expression is used since the fluids provided with energy are propelled against the outer surface of each chamber (as occurs in typical turbines with respect to the vanes).
The energy of the fluids, however, is not transferred to provide motion, as in the case of the fluid of a turbine on the vanes of the wheel, but is retained until exit from the last cavitation chamber, i.e., the innermost one, occurs, where through the gauged and angled holes the velocity acquired by the fluid is n times higher than the velocity of entry into the first cavitation chamber and the applied energy has been used to form microcells constituted by the fluids involved in the process.
The particular geometry and dimensions of each cavitation chamber, the number of holes of each chamber, the diameter and angle of the holes and therefore the energy imparted to the fluids produce intense turbulence, as desired by the assumptions on which the invention is based.
By definition, the characteristics of a turbulent motion are irregularity of the velocity of each particle that constitutes the fluid (and/or the fluids) both when they make contact with fluid streams having different velocities and when the fluids flow in contact with solid walls.
The characteristics of turbulence are, therefore, the irregularity of the velocity of each particle of fluid and the chaotic behavior of said particle with respect to the continuity and constancy of its trajectory.
Since it is impossible to determine the instantaneous values of each factor involved in the process related to the fluid particles, the system according to the invention hypothesizes a xe2x80x9cmixing pathxe2x80x9d of each particle of secondary fluid (in relation to the turbine effect, i.e., to the turbulent motion) such that the particle reaches a state in which it loses its individuality and dissolves into the whole.
The hypothesized turbine effect, which is plausible in this situation, cannot be the isotropic one, since an agitation motion which is identical in every point of the process volume is not conceivable, and also cannot be the xe2x80x9cfreexe2x80x9d one, due to the presence of walls and in any case to the vicinity of said walls both to the fluid and to each other.
However, one can hypothesize situations of xe2x80x9cconstrained turbulencexe2x80x9d, since the fluid currents are in contact with the solid walls, and of xe2x80x9canisotropic turbulencexe2x80x9d, since turbulence in the vicinity of the solid walls is certainly conceivable.
The process involves increases in the friction coefficient and in the coefficient of heat transmission between the fluid current and the solid wall.
The turbine effect and therefore the high turbulence are also helped by the mutually axially offset position of the holes of each chamber with respect to the successive one, particularly of each outer chamber with respect to the successive inner one.
The application of high-energy permanent magnets (arranged outside the primary chamber made of non-magnetic material which contains the successive chambers made of magnetizable material), although possible, has no influence, since the magnetic field would close only through the first cavitation chamber, where additionally the state of turbulence is not at its maximum level and neither is the velocity of the fluid in the hole. Even by applying ultrasonic systems with transducers of the piezoelectric or magnetostrictive type to the surface of the first chamber, the mechanical action or cavitation action on the affected fluid would not be improved when the cavitation chambers are concentric and coaxial.
Another aspect of the present invention relates to a method for producing a stabilized atomized microemulsion comprising the stages of:
a. premixing a secondary fluid with a primary fluid in order to provide a premix, for example a macrocell emulsion;
b. subjecting said premix to a succession of steps of flow at a higher average velocity, alternated with steps of flow at a lower average velocity, the high-velocity flow steps being provided at velocity values which gradually increase.
Preferably, the increase in velocity in the steps of high-velocity flow is at least fourfold, more preferably eightfold, from a first step of high-velocity flow to a last step of high-velocity flow.
The alternation of steps of flow at higher average flow velocities and of steps of flow at lower average velocities of the method according to the invention can be provided by passing a given flow-rate of premixed fluids alternately through narrower and wider flow sections.
In this case, both the narrower flow sections and the wider flow sections are gradually reduced along the path of the fluids.
An embodiment of the apparatus according to the present invention and its operation are now described in detail with reference to FIG. 1. The invention must be considered as being limited to this embodiment, which is presented merely by way of non-limitative example.